1. Field of the Invention
Aspects of the present invention relate to a multi band orthogonal frequency division multiplexing (OFDM) system and, more particularly, to a receiver performing an adaptive overlap and add (OLA) function in a multi band OFDM scheme which can determine an optimal OLA length, and a method using the receiver.
2. Description of the Related Art
A multi-band orthogonal frequency division multiplexing (OFDM) scheme generally involves an OFDM symbol hopping between frequencies among a plurality of frequency bands every predetermined symbol unit and transmitting a signal. OFDM is also used in certain wireless communication systems, such as an ultra wideband (UWB) system.
In the multi band OFDM system, a delay spread occurs in a tail of the OFDM symbol when an OFDM symbol including 128 subcarriers is received. There are as many occurrences of a loss of a header of the OFDM symbol as there are occurrences of the delay spread in the tail of the OFDM symbol. Zero padding a cyclic prefix (CP) section of the OFDM symbol has been used to prevent the loss of the header of the OFDM symbol due to the delay spread in the tail of the OFDM symbol.
The method of zero padding creates a predetermined section by zero padding a section length where the delay spread occurs in a tail of the 128 valid samples, including data in a transmission end, as required. In this case, the method of zero padding may recover the loss of the header of the OFDM symbol by adding the tail of the OFDM symbol where the delay spread occurs to the header of the OFDM symbol.
In a multi band OFDM system according to the conventional art, when there is no noise in the CP section, the OFDM symbol may be recovered when the overlap and add (OLA) length is greater than or equal to the delay spread length in an opposite position. If the OLA length is less than the delay spread length, performing an OLA operation may result in added noise. In addition, when the OLA length is less than the delay spread length, the OFDM symbol may not be completely recovered, causing an inter-carrier interference (ICI) and a decreased signal-to-noise ratio (SNR).